Rotating plunger for mercury displacement relay



July 7, 1970 v. HOROWITZ 3,519,965

- ROTATING PLUNGER FOR MERCURY DISPLACEMENT RELAY Filed Nov. 17, 1967qllmll INVENTOR VICTOR HORDWITZ 31 so j fixuhk ATTORNEYS United StatesPatent Office 3,519,965 Patented July 7, 1970 3,519,965 ROTATING PLUNGERFOR MERCURY DISPLACEMENT RELAY Victor Horowitz, Oceanside, N.Y.,assignor to Ebert Electronics Corp., New York, N.Y., a corporation ofNew York Filed Nov. 17, 1967, Ser. No. 683,913 Int. Cl. H0111 29/02 US.Cl. 335-52 10 Claims ABSTRACT OF THE DISCLOSURE A plunger type mercuryswitch is provided with a ring of Kel-F or Teflon or other low frictionplastic, extending about and protruding above the plunger, and a furtherring of the same material extending about and protruding below theplunger. The upper ring contains protrusions which serve to guide theplunger in its envelope. The lower ring includes protrusions so shapedthat each cycle of energization and de-energization of the switch causesa slight net rotation of the plunger, and the rings provide cushioningof the plunger at the ends of its travel.

BACKGROUND OF THE INVENTION The envelope of a plunger type mercuryswitch may be glass or metal, or the like. The plunger, in translatinglengthwise of the envelope during operation of the switch developsfriction with the envelope, the plunger wears, and the life of theswitch is reduced. In switches of this type small stand-off bearingsurfaces are employed, which space the plunger from the envelope. Thebearing surfaces may be of various shapes, usually being knobs, orhemispheres, and may be made of plastic material which is virtuallyfrictionless. Typical of such substances are Kel-F, which is the tradename for chlorotrifiuoroethylene sold by Minnesota Mining &Manufacturing Company, or Teflon, which is the trade name forpolytetrafluoroethylene sold by Du Pont. Prolonged life tests indicatethat a plunger tends to assume one angular position with respect to itsenvelope, so that wear takes place always identically, and life isreduced. The present invention employs stand-offs which cause a slightrotation of the plunger with each operation, the net rotation being inone sense. The offsets extend beyond the normal confines of the plunger,so that they act in substitution of the cushioning springs which arenormally employed.

The concept of providing a rotatory plunger is pro vided in the US.patent to McKinney, No. 2,973,417, but this is accomplished by a heliclcoil wound around the plunger. No cushioning action is provided.

SUMMARY OF THE INVENTION Two rings are secured about the two ends of aplunger of a mercury displacement type relay, which are shaped toprovide low friction stand-oil's and also to effect tuming of theplunger with each actuation as well as to provide cushioning at eachtermination of plunger travel.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a view in front elevation of amercury relay switch according to the invention;

FIG. 2 is an exploded view in perspective of a portion of a plungeremployed in the system of FIG. 1;

FIGS. 3 and 4 are views in perspective of alternative designs for a tabreceiving recess shown in FIG. 2;

(FIG. 5 is a view in perspective of a rotatory annulus employed in therelay switch of FIG. 1;

FIG. 6 is a top view of the structure of FIG. 5;

FIG. 7 is a side view of the structure of FIG. 5;

FIG. 8 is a view in perspective of a modification of the annulus of FIG.5;

FIG. 9 is a side view of FIG. 8; and

FIG. 10 is a view in perspective of a modification of the structure ofFIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 10 is the sealed envelope of asolenoid operated switch, and may be fabricated of glass or metal, orthe like. The operation solenoid is 11. The envelope 10 contains aquantity of mercury 12 in its lower end. A first lead 13 extends intothe envelope 10 through its bottom pinch seal 14, to a level whichassures that it will always contact the mercury 12. A second lead 15extends through pinch seal 14 and in insulated relation to the mercury12, being exposed only above the level which the mercury attains whenthe switch is not energized. An insulating cup 16 surrounds the exposedend of the lead 15, and normally contains a small quantity of mercury.The electrodes 13, 15 are then unbridged by mercury 12. when the levelof the mercury is low, and is bridged when that level is high.

A plunger 20 rides internally of the envelope 10. When undepressed andfloating, as illustrated, the level of mercury 12 is low, and whenpulled down, the level of mercury 12 is high and the switch is closed.

Plunger 20 includes an internal ceramic liner 21, surrounded except nearits top and bottom edges, 22, 23, by a ferromagnetic sleeve 24,preferably of stainless steel. Extending about the top of the liner 21and beyond it and abutting against the upper edge of sleeve 24, is anannulus 25 preferably fabricated of moldable plastic composed of ofnylon and 20% of Teflon. Teflon or nylon or Kel-F alone may be used, orthese may be impregnated, as with glass fibers, etc.

Protruding radially from the annulus 25 are preferably for equallyspaced spacers 26, preferably of triangular configuration so that theonly line contact is made between the annulus 25 and the envelope 10.

Secured about the bottom end of the ceramic liner 21 is a furtherannulus 30, which protrudes beyond liner 21 and abuts against the loweredge of sleeve 24. Spaced about the outer diameter of annulus 30 arepreferably four spacers or stand offs 31. These may have various shapes.In FIGS. 5-7, inclusive, each stand off 31 has a horizontal bottom wall33 and a slanted top; wall 34 which may make an angle of about 45 withthe bottom wall. In consequence, when the plunger is pulled down thereis no turning movement exerted on the plunger, but when the plungerrises, the plunger tends .to turn counterclockwise, as seen from below,as mercury flows along slanted top wall 34.

Variants of the shape of stand-off protrusions may be resorted to. InFIGS. 8 and 9, ribs 35 making an angle of with the horizontal may beemployed, and in FIG. 10, ribs 36 making an angle of 45 with thehorizontal may be employed. The precise angle employed is not critical;it being essentially necessary only that there be sufficient asymmetryof vertical pressures on the ribs, on upward and downward movements ofthe plunger, respectively. This asymmetry is achieved, in FIGS. 8-10, bythe differences in force required to pull down the plunger and thatwhich occurs on release of the plunger due to its buoyancy. In models ofthe system tested by us rotation occurred on both downward and upwardmotions of the plunger, but the latter was greater. So in FIG. 9 thereis a net rotation clockwise, and in FIG. 10 a net rotationcounterclockwise, as seen from above.

The plastic rings 25, 30, molded directly to ceramic liner 21, providerotation of the plunger and thereby eliminate wear of the envelope atany one location, i.e.,

wear is uniform over the inner surface of the envelope. In addition,smooth damping action occurs, which insures smooth silent operation,i.e., without chattering due to oscillation of the plunger. The usualsprings are dispensed with, which enables the plunger to proceed moredeeply into the mercury pool, increasing the buoyancy of the plungerwhile decreasing the quantity of mercury required.

In FIG. 2 is illustrated a recess 50 pre-formed in ferro-magnetic sleeve24, into which is filled a tab 51 extending from annulus 25. A similarexpedient may be adopted in respect to each of the annuli, 25 and 30, toassure that these remain fixed with respect to the plunger 20.Alternative shapes for recess 50 are illustrated at 52 and 53 of FIGS. 3and 4.

While I have described and illustrated one specific embodiment of myinvention, it will be clear that variations of the details ofconstruction which are specifically illustrated and described may berestorted to without departing from the true spirit and scope of theinvention as defined in the appended claims.

What is claimed is:

1. In a mercury switch having a cylindrical envelope containing at leasttwo contacts extending internally thereof, and having a pool of mercuryand a magnetic cylindrical plunger buoyant in the pool, the combinationof a resilient annulus secured about said plunger and axially extendingbeyond one of its ends and located only adjacent said one of its ends,said annulus having outward discrete protrusions at a greater diameterthan the outer diameter of said plunger but smaller than the innerdiameter of said envelope and being fabricated of low friction plasticnon-metallic material,

2. The combination according to claim 1 wherein said protrusions areshaped to provide asymmetrical rotary forces on movement of said plungerin opposite directions longitudinally of said envelope.

3. The combination according to claim 2 wherein said protrusions areribs making an acute angle with respect to the longituidnal axis of saidplunger of about 45.

4. The combination according to claim 1 wherein said plunger includes aceramic liner and a surrounding magnetic shell, the ends of said shellbeing spaced from an end of said liner to expose an area of liner, saidannulus being mounted on said area.

5. In a mercury switch having a cylindrical envelope containing at leasttwo contacts extending internally thereof, and having a pool of mercuryand a magnetic cylindrical plunger buoyant in the pool, the combinationof a resilient annulus secured about said plunger and extending beyondone of its ends and located only adjacent said one of its ends, saidannulus supporting means ineluding outward discrete protrusions at agreater diameter than the outer diameter of said plunger but smallerthan the inner diameter of said envelope, which extend at an angle tothe axis of said cylindrical envelope selected to provide asymmetricalrotary forces on movement of said plunger in opposite directionslongitudinally of said envelope.

6. A plunger for a mercury relay switch of the type including anenvelope containing a plunger immersed in a pool of mercury, whereinsaid plunger includes a ceramic liner, a ferromagnetic sleeve secured onsaid liner, said sleeve leaving exposed areas of said liner adjacent theends of said liner, and plastic annuli secured about said exposed areasand extending longitudinally beyond the liner in one direction and intoabutting relation with anedge of said sleeve in an opposite direction,whereby said sleeve provides a buffer for said ceramic liner and islocated by said edge of said sleeve.

7. The combination according to claim 6, wherein each of said annuliincludes discrete protrusions providing bearing surfaces between saidplunger and said envelope.

8. The combination according to claim 7 wherein said annuli arefabricated at least in part of a fiuoroethylene.

9. The combination according to claim 8 wherein the protrusions of oneof said annuli are shaped to provide surfaces oriented to generateforces tending to generate net rotation of said plunger in one sense inreseponse to longitudinal flows of said mercury longitudinally of saidone of said annuli alternately in opposite directions.

10. A plunger for a mercury relay switch of the type including anenvelope containing a plunger floating in and partially immersed in apool of mercury and constrained to be further immersed in said pool ofmercury in response to energization of a relay coil, said plunger beingferromagnetic and including an annulus, said annulus being normally atleast partially immersed in said mercury and including a configurationarranged to 1'0- tate said plunger differentially in response toreciprocating axial movements of said plunger.

References Cited UNITED STATES PATENTS 11/1936 Larson 335-52 l/1965Mitchell 335-52 US. Cl. X.R. 200-152

